where \(d_{C}(z)=\int _0^z 1/H(z) dz\)  represents the comoving distance. This form of the redshift distribution of BNS mergers is obtained according to cosmic star formation rate [1]}, [2]}, and it is also the commonly adopted form in the simulation of GW standard sirens. We simulate \(10^6\)  GW events from BNS mergers as the expectation of DECIGO in its 10-year observation [3]}. In the left panel of figure REF , we plot the number of observable events with redshift width \(\Delta z=0.1\) .
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